The present invention relates to a composite magnetic material composed of different types of magnetic materials joined together.
More specifically, the invention relates to a composite magnetic material formed as a laminate of an oxide magnetic material such as polycrystalline ferrite and a magnetic metal material such as monocrystalline Sendust. Further, the invention relates to a magnetic head having a magnetic core constructed of such composite magnetic materials joined together so as to form a magnetic head capable of magnetic recording on high coercive recording media while providing excellent high-frequency characteristics.
With the advance of electronic technology, laminated composite magnetic materials have gained a general currency in various fields of technology and are playing an important role in the field of magnetic heads used in magnetic recording.
Ferrite, which is typical of oxide magnetic material, has been used to construct magnetic cores of magnetic heads for video tape recorders (VTRs) and magnetic disc reading/writing units for use with magnetic tapes and discs, respectively, the latter including flexible ("floppy") discs. The reason for this is that oxide magnetic materials provide a high magnetic permeability in a high-frequency range (several MHz) and excellent abrasion resistance.
Recently, high coercive force recording media represented by, for instance, metal tapes and vapor-deposited metal tapes, have been developed to meet high density magnetic recording requirements. This development has been accompanied by the extensive development of magnetic materials for magnetic heads capable of use with such high coercive force recording media.
The magnetic core of the magnetic head is mainly prepared from a magnetic material, and oxide magnetic materials such as ferrite are typically used. However, as the saturation magnetic flux density of the oxide magnetic material is about 5,000 gauss, a magnetic head constructed of such a material is unusable for magnetic storage on a high coercive force recording medium having a coercive force of more than 1,000 oersteds.
Attempts have been made to use for a magnetic head a magnetic core made of a magnetic material such as Sendust having a high saturation magnetic flux density. However, the disadvantage is that, when such a magnetic metal material is used to form a magnetic head, the regenerative sensitivity of the magnetic head is reduced because of eddy-current losses in the high-frequency range.
Since a magnetic head having a magnetic core constructed of simple magnetic materials has various disadvantages, there has been proposed a magnetic head using a composite magnetic material, as shown in FIG. 1. In this magnetic head, a laminated composite magnetic material is used for the magnetic core, namely, a magnetic metal core 11 made of Sendust is sandwiched between oxide magnetic cores 12 made of ferrite to compensate for certain magnetic characteristics in the high-frequency range and improve the regenerative sensitivity of the head. The three cores are joined with silver solder.
However, such a composite magnetic material used as a magnetic core has disadvantages including a reduction in strength and difficulties in manufacture as there is required a process for sandwiching the magnetic metal core 11 between the oxide magnetic cores 12 before they are soldered.